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Feb. 21, 2019: On Nov. 14, 2018, the students of Earth to Sky Calculus launched a space weather balloon to measure increasing levels of cosmic rays in the atmosphere. At the apex of the flight, the balloon exploded and the radiation sensors parachuted back to Earth. A video camera on top of the payload recorded the pop:

These images illustrate recent findings about the physics of exploding balloons. In a Physical Review Letter entitled “Popping Balloons: A Case Study of Dynamical Fragmentation,” researchers from the Ecole Normale Supérieure in Paris report a series of laboratory experiments in which one balloon after another was popped and analyzed.

Basically, there are two ways a balloon can pop: along a single tear (the “opening regime”) or along many tears (the “fragmentation regime”). This video shows the two regimes in action. Which way the balloon decided to pop depends on the stress in the rubber membrane. When the stress is low, it can be relieved with a single tear, but when the stress is high, many tears are required to do the job.

Space weather balloons explode in the fragmentation regime, and the new research explains why. When space weather balloons are launched, they measure no more than 6 to 8 feet in diameter. By the time they reach the stratosphere, they have stretched into a sphere as wide as a house. So much stress requires many tears to release.

More information about this research is available from the American Physical Society.

Feb. 17, 2019: On Monday night, Feb. 18th, the brightest star in the night sky will disappear. It’s a rare eclipse of Sirius by asteroid 4388 Jürgenstock. As recently as two days ago, specialists thought the eclipse would be visible in a narrow corridor cutting across the central USA. New calculations, however, suggest a different path:

Sirius’s shadow will cross southern parts of Chile and Argentina, Central America and the Caribbean. This will happen on Feb. 18th between 09:11 pm PST and 09:27 pm PST.

According to David Dunham of the International Occultation Timing Association, the eclipse could last for as much as 1.8 seconds, with Sirius fading to minimum brightness for 0.2 seconds of that time. The angular diameter of Sirius is 0.006 arcseconds. Asteroid Jürgenstock is just a little wider: 0.007 arcseconds, so theoretically Sirius should be completely blocked. “But the asteroid may be a little larger or smaller than predicted, and it’s likely to be irregularly-shaped, so there is a good chance that even at the center, the star will not completely disappear,” notes Dunham.

Named after Venezuelan astrometrist Jürgen Stock, asteroid 4388 Jürgenstock orbits the sun in the inner regions of the asteroid belt between Mars and Jupiter. It is approximately 5 kilometers (3.1 miles) in diameter. Video recordings of the eclipse could help trace the shape of the distant space rock.

Jan. 22, 2019: On Jan. 21st at 04:41:43 UT, a meteoroid slammed into the Moon. We know this because so many people witnessed the explosion. It happened during a total eclipse of the Moon, visible from five continents. Dr. Fritz Helmut Hemmerich photographed the eclipse from the Canary Islands of Spain and captured the fireball:

“This is a happy shot!” says Hemmerich. “The shot just before and the shot just a few seconds later show nothing. The fireball was short-lived and I’m glad I caught it in this 2-second exposure.”

Dozens of reliable images and videos of the impact have surfaced in the days since the eclipse. Analyzing one sharp image taken by Christian Fröschlin of the Netherlands, geologist Justin Cowart has estimated the selenographic coordinates of the impact site: 29.47S, 67.77W +/- 4km. This puts it just to the west of the lunar crater Lagrange H. NASA’s Lunar Reconnaissance Orbiter may be able to use such coordinates to target its cameras and photograph the crater.

Meteoroids hit the Moon all the time. Literally. NASA has been observing impact flashes since 2005. Recently, other groups in Europe have joined the hunt. Flashes are typically recorded once every 2 to 3 hours of observing time. Impactors range in size from softballs to boulders, liberating energies equal to tons of TNT when they strike.

The rare thing about this strike is that it was photographed during a full Moon, when lunar glare usually overwhelms the glow of any fireball. During the eclipse, Earth’s shadow turned lunar day into almost-night for an hour, allowing the fireball to be seen.

Readers, were you taking pictures of the eclipse around 04:41 UT? Check your photos. You might have captured an explosion. Submit images here.

Jan. 16, 2019: Pick up your cell phone and look at it. That rectangular marvel of modern technology contains thousands of lines of code. Among them is the World Magnetic Model (WMM)–a program that helps your phone navigate. And it’s in a bit of trouble. Researchers have announced that the WMM needs an emergency update because Earth’s magnetic field is changing.

Savvy backcountry hikers have long known that compass needles don’t really point north. The magnetic north pole is displaced hundreds of miles from the true north pole and, to make matters worse, it wanders unpredictably from year to year. To find true north in the continental USA, you have to correct compass directions by as much as 20 degrees using a special “declination table.”

The World Magnetic Model is a computer program that makes this correction for you. It improves the navigation of devices ranging from nuclear submarines to common smartphones.

“The WMM is the standard magnetic model used for navigation by organizations such as NATO, the Ministry of Defence, and the US Department of Defense, and also by smartphone operating systems such as Android and iOS,” explains Will Brown of the British Geological Survey’s Geomagnetism Team, which produces the model in collaboration with NOAA of the USA.

“When you open your smartphone’s map app, you may see an arrow pointing which way you’re facing, and there’s something quite clever going on underneath,” he continues. “Your phone contains a magnetometer that is measuring the Earth’s magnetic field. In order to make sense of this information, Android and iOS operating systems use the WMM to correct the measurements to true north.”

Normally the World Magnetic Model is updated every 5 years. For decades that’s been often enough to track natural changes in our planet’s magnetism caused by fluctuations in Earth’s molten core. But suddenly things are changing faster than before.

Annual rate of change of declination for 2015.0 to 2020.0 from the World Magnetic Model (WMM2015). This information is about to be updated by a new WMM.

“Since late 2014, Earth’s core field has varied in an unpredicted, and currently unpredictable, manner [including a sudden change in declinaton called a ‘geomagnetic jerk‘ in 2014/2015],” says Brown. “The aim of the WMM is to be globally accurate within 1 degree of declination, but we were going to exceed that limit in only 3 years.” That’s why, for the first time, they are issuing an update to the WMM before the usual 5 year mark in 2020.

The new model is based data from a global network of 160 surface observatories and satellites in low-Earth orbit such as ESA’s Swarm mission. It was supposed to be released on Jan. 15th but has been delayed until Jan. 30th because of the partial shutdown of the US government.

Jan. 14, 2019: Last week, astronomers working with the ATLAS project in Hawaii announced an astonishing change to asteroid 6478 Gault. The space rock had sprouted a tail. It is now gliding through the asteroid belt giving every appearance of being a comet. On Jan. 9th, Damian Peach of Selsey UK photographed the 6478 Gault and its 400,000 kilometer-long tail:

“This is a 60 minute sequence of images, which I captured using a 20-inch telescope,” says Peach.

What happened to 6478 Gault? A clue may be found in its lineage. Asteroid Gault is a member of the Phocaeafamily, a swarm of rocks in the inner asteroid belt that formed as a result of inter-asteroid collisions some 2.2 billion years ago. The family gets its name from its most massive survivor, 25 Phocaea, which is about 75 km in diameter.

Gault’s tail may be a result of a recent collision. Researchers with the ATLAS project have looked at images of Gault in Dec. 2018 and Jan. 2019. Extrapolating its appearance backwards in time, they suggest that Gault hit another object in the asteroid belt in Nov. 2018. If that idea is correct, the tail would be debris from the crash.

Asteroid Gault was discovered in 1988 by the famous astronomer couple Carolyn and Eugene Shoemaker at the Palomar Observatory in California. For the next 30 years, the 4-km wide space rock did little to attract attention. Now, astronomers around the world are eagerly monitoring 6478 Gault to see what happens next. Stay tuned.

Readers, would you like to take pictures like Damian Peach? He’s willing to teach you how. Subscribe to his Patreon page for expert tutorials.

FULL MOON VALENTINE’S PENDANT: Poets, lovers, and artists have long known this simple truth: Nothing is more romantic than a full Moon. Now you can give the full Moon as a Valentine’s Gift–the full Moon space pendant, that is. This one flew to the stratosphere on Dec. 26, 2018, onboard an Earth to Sky Calculus cosmic ray balloon:

You can have it for $99.95. The students are selling these spherical glass pendants to support their cosmic ray ballooning program. Each one comes with a Valentine’s card showing the pendant in flight and telling the story of its journey to the edge of space and back again.

Jan. 3, 2019: Going where no nation has gone before, today China successfully landed a rover on the farside of the Moon. The Chang’e 4 lunar probe touched down in the South Pole-Aitken Basin, the largest, deepest and oldest known crater in the solar system, at 10:26 am Beijing time on Jan. 3rd.

From Earth, we can see only one side of the Moon. The other side, the farside, is perpetually hidden from view. Apollo astronauts have flown over the farside of the Moon, and many satellites have photographed the Moon from behind–revealing it to be a rugged, heavily cratered landscape startlingly different from the side we typically see.

China’s rover will be the first to explore a farside crater, probing it with ground-penetrating radar and measuring its mineral composition with an infrared spectrometer. If water is present, the rover might find it.

The first pictures of the landing site have been relayed to Earth by the Queqiao satellite, which China launched in May 21, 2018, specifically for this purpose. This is what the South Pole-Aitken Basin looks like from the inside:

The landing was remarkable. Mission control had no line-of-sight contact with the lunar farside, so the lander had to perform many complex maneuvers autonomously. (1) As it descended to an altitude of about 2 km, onboard cameras captured the shadows of objects on the lunar surface, identifying large obstacles such as rocks and craters so the probe could avoid them. (2) At 100 meters up, the probe hovered to identify smaller obstacles and measured the slopes on the surface. Its computer calculated again and selected the safest site. (3) At 2 meters above the surface, the engine stopped. Then the golden lander with a silver rover on top touched down on the desolate gray surface with four legs, throwing up some dust. The probe performed the entire landing process, lasting about 12 minutes with no intervention from ground control.

GIFTS FROM THE EDGE OF SPACE: The students of Earth to Sky Calculus are about to kick off a new year of cosmic ray balloon launches, continuing a 5-year campaign to monitor increasing levels of radiation in Earth’s atmosphere. You can help. Buy any gift item from the Earth to Sky Store and we’ll give you 10% off to celebrate the New Year.

All items in the Earth to Sky Store have flown to the edge of space onboard cosmic ray balloons. Each one comes with a greeting card showing the item in flight and telling the story of its journey. All sales support the Earth to Sky Calculus cosmic ray ballooning program and hands-on STEM research.

Jan. 2, 2019: The first high-resolution images of Ultima Thule have reached Earth following New Horizons’ historic flyby on New Year’s Day. Hot off the presses, the photos reveal a pair of roughly spherical planetestimals stuck together in the middle. The contact binary strangely resembles BB-8:

“This flyby is a historic achievement,” says New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. “Never before has any spacecraft team tracked down such a small body so far away in the abyss of space. We’re getting our first close-up look at ancient planetesimals.”

Planetestimals are the building blocks of planets. Here in the inner solar system, no pristine examples remain for us to study. They have been swallowed by planets, hammered by asteroids, and scorched by solar radiation. Ultima Thule, however, has been preserved in the deep freeze of the outer solar system for more than 4 billion years. It is truly a relic of the genesis of planets.

Mission scientists believe that Ultima Thule formed by accretion. A swarm of smaller planetesimals gathered under the pull of their own meagre gravity to form two spherical bodies, medium-sized planetesimals which themselves slowly bumped together and stuck. The result was Ultima Thule.

This is just the beginning of Ultima Thule’s revelations. First images released today have a resolution of about 140 meters per pixel. Images arriving in the days and weeks ahead will be as much as 5 times sharper, possibly revealing craters, hills, landslides, rilles and other unknowns.

New Horizons also scanned the area for tiny moons–the debris of the original swarm that gave birth to this strange object. Detections, if any, will be revealed in future transmissions from the spacecraft.

Dec. 27, 2018: The habits of a weatherman are hard to break–even on holiday. So it was that Dutch meteorologist Jacob Kuiper found himself outside on Christmas morning, looking up. What he saw amazed him. “The sky was filling with strange clouds,” says Kuiper. “At first I thought they were some form of cirrus, but these clouds were uncommonly wavy with unusual curls. When I saw the telltale flashes of color, I realized they must be polar stratospheric clouds (PSCs).”

Kuiper made a time-lapse video of the display. Note the hypnotic waves and how, at the 25 second mark, ordinary clouds may be seen scudding far below them:

Polar stratospheric clouds are not your ordinary Christmas clouds. Indeed, they have little to do with regular weather, floating so high above Earth that even airplanes cannot reach them.

Normally, the stratosphere is free of clouds–completely transparent. It’s very dry up there with a wide separation between molecules of water. When the temperature drops to around -85ºC, however, those sparse molecules begin to reluctantly gather, forming crystals of ice that become PSCs.

“I have been working in the National Meteorological Office in the central part of The Netherlands (KNMI) for 40 years,” says Kuiper. “Only twice have I seen a display of stratospheric clouds this widespread. It was thrilling. I didn’t expect the stratosphere over our country to be cold enough, but one of the stratosphere scientists in our Met. Office confirmed my idea. He also was quite surprised.”

Tiny ice crystals in PSCs can produce episodes of iridescence so brilliant that they are sometimes mistaken for auroras. The display Kuiper recorded contained only a few brief flashes of those colors–just enough for an identification.

PSCs come in two varieties: Type I contains hydrated droplets of nitric acid and sulphuric acid. These are chemicals that can destroy ozone. Indeed, an ozone hole formed over the UK in Feb. 2016 following an outbreak of Type 1 PSCs.Type II PSCs are icy and colorful, and they do little damage to the ozone layer. The clouds Kuiper witnessed may be a mixture of both.

The display was so rare that researchers in the Met Office conducted an extra round of Christmas radio soundings to probe the stratosphere. They are still processing the data, so stay tuned!

A GIFT FROM THE EDGE OF SPACE: The students of Earth to Sky Calculus are about to kick off a new year of cosmic ray balloon launches, continuing a 5-year campaign to monitor increasing levels of radiation in Earth’s atmosphere. You can help. Buy any gift item from the Earth to Sky Store and we’ll give you 10% off to celebrate the New Year.

All items in the Earth to Sky Store have flown to the edge of space onboard cosmic ray balloons. Each one comes with a greeting card showing the item in flight and telling the story of its journey. All sales support the Earth to Sky Calculus cosmic ray ballooning program and hands-on STEM research.

Dec. 23, 2018: NASA’s New Horizons spacecraft is 12 million km from Ultima Thule and closing fast. On New Year’s Day, it will fly by the mysterious Kuiper Belt Object three times closer than it buzzed Pluto in 2015 revealing … no one knows what. In fact, the mysteries have already begun.

Long range images of Ultima Thule reveal that it has no light curve. In other words, its brightness is constant.

Above: An artist’s concept of Ultima Thule, a double-lobed object in the Kuiper Belt

“It’s really a puzzle,” says New Horizons Principal Investigator Alan Stern of the Southwest Research Institute. And here’s why:

Last year, astronomers watched a distant star pass behind Ultima Thule. Starlight winked in and out in a pattern suggesting an elongated object with two bulbous lobes. Ultima Thule could be a binary system. You would expect the reflected brightness of such an object to vary as it rotates in the sunlight. Yet Ultima Thule does not behave that way.

What’s going on? New Horizons science team members have different ideas. “It’s possible that Ultima’s rotation pole is aimed almost right at the spacecraft,” speculates Marc Buie of the Southwest Research Institute. Such an alignment, however, is unlikely.

“Another explanation,” says the SETI Institute’s Mark Showalter, “is that Ultima may be surrounded by a cloud of dust that obscures its light curve–much the same way that a comet’s coma often overwhelms the light reflected by its central nucleus.”

“A more bizarre scenario is one in which Ultima is surrounded by many tiny tumbling moons,” suggests University of Virginia’s Anne Verbiscer, a New Horizons assistant project scientist. “If each moon has its own light curve, then together they could create a jumbled superposition of light curves that make it look to New Horizons like Ultima has a small light curve.”

“It’s hard to say which of these ideas is right,” Stern says. “We’ll get to the bottom of this puzzle soon – New Horizons will swoop over Ultima and take high-resolution images on Dec. 31 and Jan. 1, and the first of those images will be available on Earth just a day later. When we see those high–resolution images, we’ll know the answer to Ultima’s vexing first puzzle. Stay tuned!”

GIFTS FROM THE EDGE OF SPACE: The students of Earth to Sky Calculus are about to kick off a new year of cosmic ray balloon launches, continuing a 5-year campaign to monitor increasing levels of radiation in Earth’s atmosphere. You can help. Buy any gift item from the Earth to Sky Store and we’ll give you 10% off to celebrate the New Year.

All items in the Earth to Sky Store have flown to the edge of space onboard cosmic ray balloons. Each one comes with a greeting card showing the item in flight and telling the story of its journey. All sales support the Earth to Sky Calculus cosmic ray ballooning program and hands-on STEM research.

Nov. 19, 2018: Over the weekend, a small sunspot materialized in the sun’s northern hemisphere, then, hours later, vanished again. Such an occurrence is hardly unusual during solar minimum when sunspots are naturally small and short-lived. However, this ephemeral spot was noteworthy because its magnetic field was reversed–marking it as a member of the next solar cycle.

Shown above is a magnetic map of the sun from NASA’s Solar Dynamics Observatory on Nov. 17th. Two sunspot groups visible at 21:00 UT are inset.

Note sunspot AR2727 just north of the sun’s equator. It is a member of decaying Solar Cycle 24, the cycle that peaked back in 2012-2014. Next, compare its magnetic polarity to that of the other, unnumbered sunspot high above it. They are opposite. According to Hale’s Law, this means the two sunspots belong to different solar cycles. The high latitude sunspot appears to be a harbinger of Solar Cycle 25.

Solar cycles always mix together at their boundaries. Indeed, ephemeral sunspots possibly belonging to Solar Cycle 25 have already been reported on Dec. 20, 2016, and April 8, 2018. Now we can add Nov. 17, 2018, to list. The slow transition between Solar Cycle 24 and Solar Cycle 25 appears to be underway.

What does this mean? First, it suggests that the solar cycle is still operative. This contradicts widespread internet buzz that a Grand Minimum is in the offing, with no new sunspots expected for decades as the solar cycle grinds to a halt. Second, if patterns of previous solar cycles hold, Solar Minimum is not finished. It will probably continue to deepen in the year or so ahead even as new Solar Cycle 25 sunspots occasionally pop up, promising an ultimate end to the lassitude.